i) CRUD functions
- Must enable users to create data structures.
- Retrieve data from data structures.
- Update these data structures.
- And delete data structures
ii) Data dictionary
- Must support a repository of meta-data.
- Holds data about structure, relationships and integrity constraints.
- Holds data about names and authorization privileges associated with users.
iii) Concurrency control
- Must enable many users to access same data at the same time.
- And ensure that the database is not left in an inconsistent state when this occurs.
- Must ensure that the database can recover from software or hardware failure that damages it in some way.
Describe a data dictionary. Indicate when the data dictionary is used and by whom.
- A data dictionary is a means for recording the meta-data of some organisation.
- Also known as system catalog.
- Typically stores data about the structure of data, relationships between data items, integrity constraints expressed on data, the names and authorization privileges associated with users.
- The DD effectively implements the three-level architecture of a DBMS.
- It is a method of recording the data resources and data requirements which can be used during analysis and design as well during implementation.
- It is the main tool used by the data administrator and database administrator.